JP2003041024A - Heat-shrinkable polyester film and tubular label for cap seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film having sufficient heat shrinking force as a label for a cap seal, a high holding ratio of adhered parts and excellent shrinking finish properties and the label for the cap seal. SOLUTION: This heat-shrinkable polyester film comprises >=5 mol% of a 1,4-cyclohexanedimethanol component in 100 mol% of a polyhydric alcohol component and has a specified heat shrinkage percentage. The polyester film has <=0.70×10<8> Ω.cm value of melt resistivity at 275 deg.C and >=10% heat shrinkage percentage in the maximum shrinkage direction when a tubular label formed by adhesion of mutual film ends is primarily shrunk in hot air at 190 deg.C for 2 s by a prescribed method, then dipped in hot water at 75 deg.C for 10 s, pulled up, subsequently dipped in water at 25 deg.C for 10 s and pulled up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester film, and more particularly to a tubular label for cap seal (hereinafter simply referred to as cap seal label) for bottle containers (eg milk bottles),
The present invention relates to a heat-shrinkable polyester film that does not cause peeling of the adhesive part of the label even after shrinkage, and has little occurrence of defects such as wrinkles, shrinkage spots, distortion, and jumping due to shrinkage, and a tubular label for a cap seal. .

[0002]

2. Description of the Related Art In recent years, containers such as bottles for beverages, foods, etc. have been provided with a seal called a cap seal on their stoppers or lids. The cap seal is provided not only for the purpose of imparting decorativeness, but also for the purpose of preventing contamination of poisonous substances and the like because it proves that the stopper or lid is unopened.

A heat-shrinkable film made of polyvinyl chloride, polystyrene or the like has been mainly used for a label for a cap seal as in a normal label, but a polyvinyl chloride film generates hydrogen chloride gas when incinerated. Or have problems such as causing dioxins.
Further, since the polystyrene film is poor in solvent resistance, it is necessary to use an ink having a special composition for printing. Further, when collecting and recycling the PET bottle, it is necessary to separate the label of the resin other than PET such as polyvinyl chloride and polystyrene from the container. Therefore, it is desired to apply a heat-shrinkable polyester film that does not have these problems to a cap seal label.

By the way, for the cap seal, a label prepared by rolling a heat-shrinkable film of a predetermined size into a tube and adhering the ends to each other to form a tubular body and further cutting this is used. . The cap sealing method is to cover the label directly on the container and shrink it in one step, or to cover the label on a metal mold and heat shrink (primary shrink) to mold the preform, There are two general two-step methods in which the container is covered and further contracted (secondary contraction). Either way,
It is not desirable that the adhesive portion of the label be peeled off due to heat shrinkage, and in order to improve production efficiency, it is essential to improve the retention rate of the adhesive state of the adhesive portion of the label. The peeling of the adhesive portion refers to, for example, peeling of the lower portion of the adhesive portion when heat-shrinking as shown in FIG. 2A, or peeling of the adhesive portion upper portion as shown in FIG. 2B. . In addition, as will be described in detail in a later example, in FIG. 2, a cap seal label is placed on a metal mold, and 190 ° C. × 2 seconds (hot air).
Although an example of a defect that occurs when a preform is molded by heat shrinking under the conditions described above is shown, such a defect may occur in the final product.

On the other hand, the characteristics relating to the shape of the label when the label is thermally shrunk are also important. That is, the occurrence of defects such as insufficient shrinkage of the label, wrinkles, distortion, and jumping (a state in which the label covers almost the entire upper surface of the cap) is undesirable. FIG. 2C shows a jumping up state. It can be seen that the label covers almost the entire upper surface of the metal mold, and the lower part of the metal mold is exposed more than in the other examples, resulting in misalignment. 2D shows an example in which wrinkles have occurred, and FIG. 2E shows an example in which shrinkage is insufficient. Since the label (preform) in which these defects have occurred cannot be used for the cap seal, it is necessary to suppress the occurrence of these defects as much as possible. Further, even when the heat shrinks in one step, the occurrence of such a defect deteriorates the shrink finish property, which is not preferable. In particular, when capping a food container that is disliked with water with hot air, the hot air tunnel has a lower thermal efficiency than the steam tunnel, and thus there is a problem that the above-mentioned defects are likely to occur. In addition, when a two-step heat shrinking process using a preform is performed, the cap seal label has to shrink further after the primary shrinkage, and thus exhibits a unique heat shrinking behavior different from that of the conventional heat shrinkable film. There is a need.

Further, if the cap seal label has a non-uniform thickness, there is a problem that a trouble is likely to occur when the label is attached to the cap. Therefore, production of a film having a particularly small thickness distribution is desired. Here, the polyester film is usually manufactured by cooling a melt-extruded film with a casting roll and then stretching the film. Then, during this cooling, the film and the casting roll are electrostatically brought into close contact with each other to enhance cooling efficiency and control the thickness distribution. In order to electrostatically adhere the film to the roll, many charge carriers may be present on the surface of the molten film immediately after extrusion before contacting the roll, and,
To increase the number of charge carriers, it is effective to modify the polyester to reduce its specific resistance. However, it is not so easy to reduce the specific resistance depending on the composition of the polyester, and great efforts are made.

[0007]

The present invention has been made by paying attention to various circumstances as described above, and has a sufficient heat shrinkage force as a label for a cap seal, and a retention rate of an adhesive portion. It is an object of the present invention to provide a heat-shrinkable polyester film and a label for cap seal which are high and have excellent shrink finish.

[0008]

The present invention provides a polyhydric alcohol component 10 in a heat-shrinkable polyester film.
Of 0 mol%, 1,4-cyclohexanedimethanol component is 5 mol% or more, and for the sample of the heat-shrinkable polyester film cut into a square shape of 10 cm × 10 cm, the following (A), (B) and The heat shrinkage percentage of (C) is (A): 15 to 40%, (B): 45 to 67%,
(C): 8% or less, (A): thermal contraction rate in the maximum contraction direction when immersed in warm water of 65 ° C. for 10 seconds and pulled up, and then immersed in water of 25 ° C. for 10 seconds and pulled up, (B): Heat shrinkage in the maximum shrinking direction when immersed in warm water of 85 ° C for 10 seconds and then pulled up, then immersed in water of 25 ° C for 10 seconds, (C): In warm water of 85 ° C Heat shrinkage in a direction orthogonal to the maximum shrinkage direction when immersed in water for 10 seconds and pulled up, and then immersed in water at 25 ° C. for 10 seconds, and the melt specific resistance value at a temperature of 275 ° C. is 0.70 × 10 ^8.
Ω · cm or less, the tube-shaped label formed by adhering the film ends to each other is first shrunk in hot air at 190 ° C. for 2 seconds by a predetermined method, and then in hot water at 75 ° C. for 10 seconds.
The heat shrinkage rate in the maximum shrinkage direction is 10% when immersed in water at 25 ° C for 10 seconds and then pulled up.
The above is the summary.

The heat-shrinkable polyester film having the above-mentioned properties has a large residual shrinkage after primary shrinkage, a high retention of the adhesive portion, and excellent shrink finish (suppression of shrinkage whitening, shrinkage unevenness, It suppresses wrinkles, distortion, and jumps up, etc., and can make the cap seal look good after heat shrinking. Moreover, it is excellent in electrostatic adhesion, improves the quality of the film (suppression of pinner bubbles, etc.), and can make the thickness distribution uniform, thus reducing shrinkage defects and appearance defects.

As a measure of the retention rate of the adhesive portion, the adhesive state retention rate of the adhesive portion after the primary contraction of the tubular label is 95.
% Or more is preferable. Further, as a measure of the distribution of the thickness of the film, when the displacement of the thickness with respect to the maximum shrinkage direction of the film is measured using a test piece having a length of 50 cm in the maximum shrinkage direction and a width of 5 cm, it is represented by the following formula. The thickness distribution is preferably 5% or less. Thickness distribution = (maximum thickness-minimum thickness) / average thickness x 100

The ratio of 1,4-cyclohexanedimethanol to 100 mol% of the polyhydric alcohol component is 1
It is preferably 0 to 80 mol%. 1,4 in this range
-By controlling the ratio of cyclohexanedimethanol, it is possible to increase the shrinkage force after the primary shrinkage, and further it is possible to suppress shrink finish properties, especially shrink whitening.

The film is made of an alkaline earth metal atom M.
² and a phosphorus atom P are preferably contained [content: the alkaline earth metal atom M ² is, for example, 40 to 40].
About 0 ppm (mass standard), the phosphorus atom P is, for example, 6
0 to 600 ppm (mass standard)], the mass ratio of the alkaline earth metal atom M ² in the film to the phosphorus atom P (M ²
/ P) is preferably 1.2 to 5.0. When the mass ratio (M ² / P) is controlled within the above range, not only the melting specific resistance value can be reduced but also foreign matters in the film can be reduced. In addition, the film contains 5 to 10 alkali metal atoms M ¹ .
It is preferable to contain about 0 ppm (mass standard) because the melting specific resistance value can be further reduced.

The present invention also includes a tubular label for a cap seal obtained by adhering the ends of the heat-shrinkable polyester film of the present invention.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-shrinkable polyester film of the present invention is a film obtained by using a single polyester or a plurality of polyesters, and contains a dicarboxylic acid component constituting the polyester and a polyhydric alcohol component. . The polyhydric alcohol component is prepared so as to contain 5 mol% or more of 1,4-cyclohexanedimethanol component with respect to the entire polyhydric alcohol component (100 mol%). By setting the proportion of the 1,4-cyclohexanedimethanol component to 5 mol% or more, the degree of amorphization of the film can be increased, and the heat shrinkage force required for the cap seal label can be obtained. If it is less than 5 mol%,
The heat shrink force required for a cap seal label cannot be obtained. In order to exhibit tear resistance, strength, heat resistance, etc. as a film, the polyester film must have a crystalline unit (such as ethylene terephthalate unit), but the crystalline unit alone can Since the shrinkability is low, in the present invention, 1,4-cyclohexanedimethanol is used as an essential component to adjust the composition of the polyester film, increase the degree of amorphization, and enhance the heat shrinkability.

The use of the 1,4-cyclohexanedimethanol component makes it possible to enhance shrink finish properties (suppression of shrinkage whitening, shrinkage unevenness, wrinkles, strain, jumping, etc.). To manufacture a label for a cap seal, a heat-shrinkable film is often adhered using a solvent (tetrahydrofuran, 1,3-dioxolane, etc.), but the ratio of 1,4-cyclohexanedimethanol component is 5 mol. When it is at least%, the solvent adhesiveness is improved, and the retention rate (described later) of the adhesive portion can be increased.

Further, since the cap seal label is often used without being printed, it is preferably excellent in transparency from the viewpoint of appearance. However, the shrinkage whitening phenomenon is likely to occur when heat-shrinking in a hot-air tunnel or when heat-shrinking after storing for a long time in an atmosphere of 30 ° C. or higher. It is considered that this shrinkage whitening phenomenon may occur because the molecular chain of the polyester is partially crystallized and the light refractive index of the crystal part is different from that of the amorphous part. Shrinkage whitening is a phenomenon unfavorable as a label for a cap seal because it reduces transparency.

However, the present inventors can remarkably suppress the above-mentioned shrinkage whitening by further increasing the ratio of the 1,4-cyclohexanedimethanol component to 10 mol% or more in 100 mol% of the polyhydric alcohol component. I found that.
Furthermore, shrinkage spots can be significantly suppressed. The amount of the 1,4-cyclohexanedimethanol component is more preferably 12 mol% or more, further preferably 14 mol% or more.

On the other hand, polyhydric alcohol component 100 mol%
It is desired that the content of the 1,4-cyclohexanedimethanol component be suppressed to 80 mol% or less. If the amount of 1,4-cyclohexanedimethanol component is too much, the tear resistance, heat resistance, etc. of the film are deteriorated, which is not preferable. Therefore,
The total amount of these is more preferably 70 mol% or less, 60
It is more preferably not more than mol%.

In the film of the present invention, the above 1,4-
The other polyhydric alcohol component that can be used in addition to the cyclohexanedimethanol component may be a diol component or a trihydric or higher alcohol component. The diol forming the diol component includes ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 2,2-diethyl-
1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 1,9-nonanediol, 1,10-decanediol, etc. Alkylene glycol; diethylene glycol, triethylene glycol,
Polyethylene glycol, polypropylene glycol,
Ether glycols such as polyoxytetramethylene glycol, alkylene oxide adducts of bisphenol compounds or derivatives thereof; dimer diol and the like are included. Trihydric or higher alcohols include trimethylolpropane, glycerin, pentaerythritol and the like. Among them, ethylene glycol is preferable for the crystalline unit, and as the unit for increasing the non-crystallinity,
Neopentyl glycol is preferred.

As the polyvalent carboxylic acids forming the polyvalent carboxylic acid component, aromatic dicarboxylic acids, ester-forming derivatives thereof, aliphatic dicarboxylic acids and the like can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-1,4-or-
2,6-dicarboxylic acid, 5-sodium sulfoisophthalic acid and the like can be mentioned. Examples of ester derivatives include derivatives such as dialkyl esters and diaryl esters. Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid and succinic acid.

In addition to the above polycarboxylic acids, p-
An oxycarboxylic acid such as oxybenzoic acid or a trivalent or higher carboxylic acid such as trimellitic anhydride or pyromellitic dianhydride may be used in combination as necessary.

Further, the polyester does not necessarily have to be produced from the above-mentioned polyvalent carboxylic acids and polyhydric alcohols, and a polyester unit may be formed by ring-opening polymerization of lactones (ε-caprolactone etc.). The combined use of lactones has the function of increasing the degree of amorphism. In addition,
When calculating the ratio (mol%) of each component in the polyhydric carboxylic acid component and the polyhydric alcohol component, the ring-opening component of the lactone corresponds to both the polyhydric carboxylic acid component and the polyhydric alcohol component. Calculate as.

Considering the tear resistance, strength, heat resistance and the like of the film, it is preferable to select the polyester so that the crystalline unit (ethylene terephthalate unit etc.) in the polyester is 20 mol% or more. Therefore,
The terephthalic acid component is preferably 20 mol% or more in 100 mol% of the polycarboxylic acid component. In addition, the ethylene glycol component is 2 in 100 mol% of the polyhydric alcohol component.
It is preferably 0 mol% or more. The crystalline unit is
30 mol% or more is more preferable, and 40 mol% or more is further preferable. However, in the present invention, since the 1,4-cyclohexanedimethanol component is 5 mol% or more in 100 mol% of the polyhydric alcohol component, the ethylene glycol component is 95 mol% or less. Incidentally, it is of course possible to blend and use polyesters having various compositions so as to fall within the above preferable range.

The heat-shrinkable polyester film of the present invention needs to exhibit the following heat-shrinkable properties. This is to ensure the heat shrinkage force required for the cap seal label. Specifically, regarding the sample of the heat-shrinkable polyester film cut into a square shape of 10 cm × 10 cm, the heat shrinkage rates of the following (A), (B) and (C) are as follows:
(A): 15-40%, (B): 45-67%,
(C): Must be 8% or less. Here, (A): thermal shrinkage in the maximum shrinking direction when immersed in warm water of 65 ° C. for 10 seconds and pulled up, and then immersed in water of 25 ° C. for 10 seconds and pulled up, (B): 85 ° C. Thermal contraction rate in the maximum shrinking direction when immersed in warm water for 10 seconds and then pulled up, then immersed in water at 25 ° C for 10 seconds, (C): immersed in warm water at 85 ° C for 10 seconds and pulled up, Then, the heat shrinkage rate in the direction orthogonal to the maximum shrinkage direction when immersed in water at 25 ° C. for 10 seconds and pulled up.

The heat shrinkage in the maximum shrinkage direction means the heat shrinkage in the direction in which the sample is most shrunk, and the maximum shrinkage direction is the vertical or horizontal direction (or diagonal direction) of the square. It is decided by the length. The heat shrinkage rate in the direction orthogonal to the maximum shrinkage direction is the heat shrinkage rate in the direction orthogonal to the maximum shrinkage direction of the sample defined as above.
The heat shrinkage rate (%) is 25 ° C. ± 0.5 ° C. after the sample having a size of 10 cm × 10 cm is immersed in the warm water at the respective temperatures of ± 0.5 ° C. for 10 seconds in a non-loaded state to cause the heat shrinkage. The length of the film in the longitudinal and transverse directions (or diagonal direction) after being dipped in water for 10 seconds in an unloaded state was measured, and the following equation: heat shrinkage rate = 100 × (length before shrinkage−after shrinkage Length) ÷
It is a value obtained according to (length before shrinkage).

A film in which all the heat shrinkage percentages of (A), (B) and (C) satisfy these ranges generate a defect as shown in FIG. 2 even when used as a cap seal label. It is possible to secure a beautiful shrink finish appearance.

In the film (A) having a heat shrinkage of less than 15%, the heat shrinking step (the heat shrinking step of covering the container from the beginning and shrinking it in one step, the primary shrinkage in the case of undergoing two steps of heat shrinkage) In any of the secondary shrinking steps), the shrinkage rate under low temperature conditions becomes insufficient. But,
If it exceeds 40%, the label jumps up, which is not preferable. The more preferable lower limit of the heat shrinkage ratio of (A) is 20%, and the more preferable upper limit thereof is 35%.

Further, the above-mentioned (B) film having a heat shrinkage rate of less than 45% is not preferable because shrinkage tends to occur insufficiently. On the other hand, a film of more than 67% is not preferable because the force of further shrinking after heat shrinking is too large and jumping is likely to occur. The more preferable lower limit of the heat shrinkage ratio of (B) is 50%, and the upper limit thereof is 65%.

In the case of the film (C) having a heat shrinkage ratio of more than 8%, the amount of shrinkage in the direction in which shrinkage is not necessary becomes large, and the amount of film required when used for a label or the like becomes large, so that it is economical. It is not preferable from a technical viewpoint. The more preferable upper limit of the heat shrinkage ratio of (C) is 6%. A film that does not shrink during heat shrinkage and extends in a direction orthogonal to the maximum shrinkage direction of the film easily causes wrinkles in the heat shrinkage step. Therefore, the preferable lower limit of the heat shrinkage ratio of (C) is 0%, and the more preferable lower limit thereof is 1%.
Is.

The heat-shrinkable polyester film of the present invention must have a somewhat high residual shrinkage ratio after the primary shrinkage. This is because when the preform is molded by the primary shrinkage and then covered by an actual container for the secondary shrinkage, the shrinkage force must be exerted also in the secondary shrinkage.
In the present invention, the residual shrinkage rate was evaluated as follows. The heat-shrinkable film (unshrinked) is left in a thermo-hygrostat at a temperature of 30 ± 1 ° C. and a humidity of 85 ± 2% for 250 hours and then taken out, and one end of one end of the film is removed using a tubular molding device. 2 1,3-dioxolanes slightly inside from the edge
It is applied in a width of mm, the film is immediately rolled, the ends are overlapped and bonded, and processed into a tubular body. This is cut, and a label 1 having a bent diameter (half of the circumference of the tube) of 87 mm and a length of 53 mm as shown in FIG. The maximum contraction direction is the circumferential direction of the label. As shown in FIG. 1B, a metal cylinder 2 having a diameter of 46 mm
(Hatch part) and heat shrink in hot air at 190 ° C. for 2 seconds. At this time, when L ₁ in FIG. 1B is 47 mm, that is, when the film is contracted by covering the metal cylinder 2 with a film having a length of 6 mm protruding above the metal cylinder 2, L ₁ is reduced. 47 m
A preform body having m and L ₂ of 6 mm and a width of the overlapping portion of the adhesive portion of 5 mm is formed. The heat shrinking condition of 190 ° C. for 2 seconds is a convenient condition for giving a heat amount in a short time, which is similar to that used in preform molding (primary shrinkage) in an actual production line. Cut off the adhesive part of the label after shrinkage, cut out the sample so that the maximum shrinkage direction (circumferential direction) of the label is 100 mm and the direction orthogonal to this maximum shrinkage direction is 40 mm, and warm water at 75 ± 0.5 ° C After heat-shrinking by immersing it in a non-loaded state for 10 seconds and then immersing it in water at 25 ° C ± 0.5 ° C for 10 seconds in a non-loaded state, the length in the maximum shrinking direction is measured, and the residual shrinkage rate (% ) Is calculated by the following formula. Residual shrinkage rate = 100 x (length before shrinkage-length after shrinkage)
÷ (length before shrinkage)

In the present invention, the residual shrinkage ratio must be 10% or more. If the residual shrinkage is less than 10%, the shrinkage is insufficient in the secondary shrinkage step after preform molding, which leads to poor appearance of the cap seal. The residual shrinkage rate is not particularly limited as long as it is 10% or more, but there is a limit to the residual force of the shrinkage force, and the upper limit is about 20% at most.

The heat-shrinkable polyester film of the present invention is excellent not only in the above-described shrinkage characteristics and shrink finish, but also in the uniformity of thickness distribution, productivity and film quality because of its low melt resistivity. . That is, the heat shrinkable polyester film of the present invention has a melt specific resistance of 0.70.
× 10 ⁸ Ω · cm or less. When the melt specific resistance value is small, the electrostatic adhesion of the film to the roll can be increased when the film melt-extruded from the extruder is cooled by the casting roll. If the thickness of the label for cap seal is not uniform, there is a problem that troubles are likely to occur when it is attached to the cap, and it is desired to manufacture a film with a particularly small thickness distribution, but to improve electrostatic adhesion. Thus, a film having a small thickness distribution can be obtained. Further, when the electrostatic adhesion is enhanced, the stability of cooling and solidification can be enhanced, and the casting speed (production rate) can be increased. The melting specific resistance value is preferably 0.65 × 10 ⁸ Ω · cm or less, more preferably 0.60 × 10 ⁸ Ω · cm or less.

Further, if the melting specific resistance value is low and the electrostatic adhesion is high, the film quality can be improved. That is, when the electrostatic adhesion is low, cooling and solidification of the film may be incomplete, air may locally enter between the casting roll and the film, and pinner bubbles (streak defects) may occur on the film surface. On the other hand, when the electrostatic adhesion is excellent, the pinner bubble can be reduced and the film appearance can be enhanced.

In addition, when the melting specific resistance value is sufficiently low and the electrostatic adhesion is sufficiently high, the film thickness can be made uniform. That is, when the electrostatic adhesion to the casting roll is low, the thickness of the cast unstretched film material becomes nonuniform, and in the stretched film obtained by stretching this unstretched film, the nonuniformity in thickness is further expanded. On the other hand, when the electrostatic adhesion is sufficiently high, the thickness of the stretched film can be made uniform. The thickness uniformity can be evaluated by the thickness distribution represented by the following formula. Thickness distribution (%) = 100 × (maximum thickness−minimum thickness) / average thickness

The maximum thickness, the minimum thickness, and the average thickness were measured by cutting a sample having a width of 5 cm so that the length in the maximum shrinkage direction of the film was 50 cm, and using a contact thickness meter, the thickness in the maximum shrinkage direction was measured. Can be determined by measuring the displacement of

The thickness distribution is preferably 5% or less. It is more preferably 4% or less. If the thickness distribution is too large, spots and wrinkles are likely to occur during contraction. In addition, when processing the film into a tubular body by solvent bonding, it becomes difficult to overlap the bonded parts, or there is a partial difference in the winding hardness when the film is wound into a roll, causing slack in the film. Wrinkles occur and the appearance of the film is greatly impaired.

When the thickness distribution is made sufficiently small, it is desirable to optimize the stretching conditions such as the stretching ratio of the film, the preheating temperature during stretching, and the stretching temperature, in addition to enhancing the electrostatic adhesion. .

In order to control the melt specific resistance value of the film within the above range, it is desirable that the film contains an alkaline earth metal compound and a phosphorus-containing compound. The melting specific resistance value can be lowered only by the alkaline earth metal compound, but the coexistence of the phosphorus-containing compound can markedly lower the melting specific resistance value. It is not clear why the combination of the alkaline earth metal compound and the phosphorus-containing compound can significantly reduce the melting specific resistance value, but the inclusion of the phosphorus-containing compound can reduce the amount of foreign matter and can improve the charge carrier. It is presumed that the amount can be increased.

The content of the alkaline earth metal compound in the film is, for example, 40 ppm (mass basis) or more, preferably 50 pp, based on the alkaline earth metal atom M ^2.
m (mass basis) or more, more preferably 60 ppm (mass basis) or more. If the amount of the alkaline earth metal compound is too small, the melt specific resistance value cannot be lowered. Even if the content of the alkaline earth metal compound is excessively large, the effect of reducing the melting specific resistance value is saturated, and the adverse effects such as the generation of foreign matter and the coloring are rather large. Therefore, the content of the alkaline earth metal compound is, for example, 400 ppm (mass reference) or less, preferably 350 ppm (mass reference) or less, and more preferably 300 ppm (mass reference) or less, based on the alkaline earth metal atom M ^2. Is.

The content of the phosphorus compound in the film is, for example, 10 ppm (mass basis) based on the phosphorus atom P.
The above is preferably 15 ppm (mass basis) or more, more preferably 20 ppm (mass basis) or more. If the amount of the phosphorus compound is too small, it is not possible to sufficiently lower the melting specific resistance value, and it is also impossible to reduce the amount of foreign matter produced. Even if the content of the phosphorus compound is too large, the effect of reducing the melting specific resistance value is saturated. Furthermore, since the production of diethylene glycol is promoted and it is difficult to control the production amount, the physical properties of the film may be different from those expected. Therefore, the content of the phosphorus compound is, for example, 500 ppm (mass basis) or less, preferably 450, based on the phosphorus atom P.
ppm (mass basis) or less, more preferably 400 pp
It is m (mass standard) or less.

When the melting specific resistance of the film is lowered with an alkaline earth metal compound and a phosphorus compound, the mass ratio of the alkaline earth metal atom M ² to the phosphorus atom P (M ²
/ P) is preferably 1.2 or more (preferably 1.3 or more, more preferably 1.4 or more). By setting the mass ratio (M ² / P) to 1.2 or more, the melting specific resistance value can be significantly reduced. When the mass ratio (M ² / P) exceeds 5.0, the amount of foreign matter produced increases or the film is colored. Therefore, the mass ratio (M ² / P) is
It is 5.0 or less, preferably 4.5 or less, and more preferably 4.0 or less.

In order to further reduce the melt specific resistance value of the film, it is desirable to add an alkali metal compound in the film in addition to the alkaline earth metal compound and the phosphorus-containing compound. Even if the alkali metal compound is contained alone in the film, the melting specific resistance value cannot be lowered, but by adding it to the coexisting system of the alkaline earth metal compound and the phosphorus-containing compound, the melting specific resistance value can be remarkably lowered. You can Although the reason is not clear,
By forming a complex with an alkali metal compound, an alkaline earth metal compound, and a phosphorus-containing compound,
It is presumed that the melting specific resistance value is lowered.

The content of the alkali metal compound in the film is, for example, 0 p based on the alkali metal atom M ^1.
It is pm (mass standard) or more, preferably 5 ppm (mass standard) or more, more preferably 6 ppm (mass standard) or more, and particularly 7 ppm (mass standard) or more. Even if the content of the alkali metal compound is too large, the effect of reducing the melting specific resistance value is saturated, and the amount of foreign matter generated is increased. Therefore, the content of the alkali metal compound is, for example, 100 pp, based on the alkali metal atom M ^1.
m (mass standard) or less, preferably 90 ppm (mass standard) or less, and more preferably 80 ppm (mass standard) or less.

Examples of the alkaline earth metal compound include hydroxides, alkoxides, aliphatic carboxylic acid salts (acetic acid salts, butyric acid salts, etc., preferably acetic acid salts) of alkaline earth metal, and aromatic carboxylic acid salts (benzoic acid). Salt), a salt with a compound having a phenolic hydroxyl group (salt with phenol, etc.) and the like. Examples of the alkaline earth metal include magnesium, calcium, strontium, barium and the like (preferably magnesium). Preferred alkaline earth metal compounds include magnesium hydroxide, magnesium methoxide, magnesium acetate, calcium acetate, strontium acetate, barium acetate and the like, especially magnesium acetate. The alkaline earth metal compounds may be used alone or in combination of two or more.

Examples of the phosphorus compound include phosphoric acids (phosphorus
Acid, phosphorous acid, hypophosphorous acid, etc.) and their esters
(Alkyl ester, aryl ester, etc.), and
Lucylphosphonic acids, arylphosphonic acids and their
Ester (alkyl ester, aryl ester, etc.)
Can be mentioned. Preferred phosphorus compounds include phosphoric acid and lithium.
Aliphatic ester of acid (alkyl ester of phosphoric acid, etc.)
For example, phosphoric acid monomethyl ester, phosphoric acid monoethyl ester
Phosphoric acid mono C such as ester and monobutyl phosphate
_1-6Alkyl ester, dimethyl phosphate, phosphorus
Phosphorus such as acid diethyl ester and phosphoric acid dibutyl ester
Acid di C_1-6Alkyl ester, trimethyl phosphate ester
, Phosphoric acid triethyl ester, phosphoric acid tributyl ester
Tellurium phosphate C_1-6Alkyl ester, etc.), phosphorus
Aromatic esters of acids (triphenyl phosphate, triphosphate
Mono-, di- or tri-C of phosphoric acid such as cresyl_6-9Ants
Ester), aliphatic ester of phosphorous acid (phosphorus
Alkyl esters of acids, etc .; for example, trimethyl phosphite
Mono, di of phosphorous acid, such as tributyl phosphite,
Is a bird C_1-6Alkyl ester, etc.), alkyl phosphone
Acid (C such as methylphosphonic acid, ethylphosphonic acid, etc._1-6A
Alkyl phosphonate, alkyl phosphonate
Tell (Dimethyl methylphosphonate, Diethyl ethylphosphonate
C such as methyl_1-6Alkylphosphonic acid mono or di C
_1-6Alkyl ester, etc.), arylphosphonic acid alk
Luester (dimethyl phenylphosphonate, phenylpho
C such as diethyl sulfonate_6-9Arylphosphonic acid mono
Or the C_1-6Alkyl ester, etc.), aryl phospho
Acid aryl ester (diphenyl phenylphosphonate
Such as C _6-9Arylphosphonic acid mono or di C_6-9Ants
And the like). Particularly preferred phosphatization
The compound is phosphoric acid, trialkyl phosphate (trimethyphosphate
Le etc.). These phosphorus compounds may be used alone or in two kinds.
The above can be used in combination.

Examples of the alkali metal compound include alkali metal hydroxides, carbonates, aliphatic carboxylates (acetate, butyrate, etc., preferably acetate), aromatic carboxylates (benzoate), Examples thereof include salts with compounds having a phenolic hydroxyl group (salts with phenol, etc.). Examples of the alkali metal include lithium, sodium, potassium and the like (preferably sodium). Preferred alkaline earth metal compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium acetate, sodium acetate,
Includes potassium acetate and the like, especially sodium acetate.

The polyester can be produced by melt polymerization by a conventional method, but an oligomer obtained by directly reacting a dicarboxylic acid with a glycol is subjected to polycondensation,
Examples include so-called direct polymerization method, so-called transesterification method in which dimethyl ester of dicarboxylic acid and glycol are subjected to transesterification reaction and then polycondensation, and any production method can be applied. Further, it may be a polyester obtained by another polymerization method. The degree of polymerization of polyester is 0.5 to 1.3d in terms of intrinsic viscosity.
It is preferably 1 / g.

As the polymerization catalyst, various conventional catalysts can be used. For example, titanium catalysts, antimony catalysts, germanium catalysts, tin catalysts, cobalt catalysts, manganese catalysts, etc., preferably titanium catalysts ( Examples thereof include titanium tetrabutoxide), antimony-based catalysts (antimony trioxide, etc.), germanium-based catalysts (germanium dioxide, etc.), cobalt-based catalysts (cobalt acetate, etc.), and the like.

The timing of adding the alkali metal compound, the alkaline earth metal compound, and the phosphorus-containing compound is not particularly limited, and may be before the esterification reaction, during the esterification, from the end of the esterification to the start of the polymerization step, during the polymerization, and the polymerization. Although it may be any subsequent stage, it is preferably any stage after the esterification step, more preferably between the end of the esterification and the start of the polymerization step. When the alkaline earth metal compound and the phosphorus-containing compound (and, if necessary, the alkali metal compound) are added after the esterification step, the amount of foreign substances generated can be reduced as compared with the case where they are added before that.

If necessary, fine particles of silica, titanium dioxide, kaolin, calcium carbonate or the like may be added to the film raw material, and further, an antioxidant, an ultraviolet absorber, an antistatic agent, a coloring agent, an antibacterial agent. Etc. can also be added.

The polyester film can be obtained by a publicly known method described later. In the heat shrinkable polyester film, a means for controlling the polyhydric alcohol component within a specific range is a copolyester (copolyester). And a method of blending a plurality of polyesters [for example, a method of blending a plurality of different homopolyesters; a method of blending a homopolyester (polyethylene terephthalate etc.) and a copolyester; There is a method of blending copolyester].

In the system in which the copolyester is used alone, the copolyester containing the polyhydric alcohol component having the above specific composition may be used. On the other hand, the method of blending a plurality of polyesters can be preferably used because the characteristics of the film can be easily changed only by changing the blending ratio and industrial production of various kinds of films can be supported.

As a specific method for producing a film, the raw material polyester chips are dried using a dryer such as a hopper dryer, a paddle dryer or the like, or a vacuum dryer,
It is extruded into a film at a temperature of 200 to 300 ° C. using an extruder. Alternatively, the undried polyester raw material chips are similarly extruded into a film shape while removing water in a vent type extruder. Any existing method such as a T-die method or a tubular method may be adopted for extrusion. The extruded molten film is rapidly cooled with a casting roll to obtain an unstretched film.

In the present invention, an electrode is arranged between the extruder and the casting roll, a voltage is applied between the electrode and the casting roll, and the film is electrostatically adhered to the roll.

The unstretched film is stretched to produce a heat-shrinkable polyester film. Since it is practical in terms of production efficiency that the maximum shrinkage direction is the film lateral (width) direction during the stretching treatment, an example of the stretching method in which the maximum shrinkage direction is the lateral direction will be shown below. Even when the maximum shrinkage direction is the longitudinal (longitudinal) direction of the film, the stretching can be carried out according to a normal operation such as changing the stretching direction by 90 ° in the following method.

Focusing on making the thickness distribution of the heat-shrinkable polyester film uniform, it is preferable to carry out a preliminary heating step prior to the stretching step when stretching in the transverse direction using a tenter or the like. In the heating step, the coefficient of thermal conductivity is 0.00544 J / cm ² · sec · ° C (0.
0013 calories / cm ² · sec · ° C) or less, the film surface temperature is Tg + 0 ° C to Tg at a low wind speed.
It is preferable to heat to a certain temperature within the range of + 60 ° C. The Tg represents a glass transition temperature.

Stretching in the transverse direction is Tg-20 ° C. to Tg + 4.
At a predetermined temperature within the range of 0 ° C., the film is stretched 2.3 to 7.3 times, preferably 2.5 to 6.0 times. Then, 50 ℃ ~ 1
Heat treatment is performed at a predetermined temperature within the range of 10 ° C while stretching 0 to 15% or relaxing 0 to 15%, and 40 ° C to 1
It is preferable to further perform heat treatment at a predetermined temperature within the range of 00 ° C.

In this transverse stretching step, it is preferable to use equipment capable of reducing the fluctuation of the film surface temperature. That is, in the stretching step, a preheating step before stretching, a stretching step, a heat treatment step after stretching, a relaxation treatment,
Although there is a re-stretching step, etc., in particular, in the preheating step, the stretching step and the heat treatment step after stretching, the fluctuation range of the surface temperature of the film measured at an arbitrary point is within the average temperature ± 1 ° C. Average temperature ±
More preferably, it is within 0.5 ° C. This is because if the fluctuation range of the surface temperature of the film is small, the film is stretched and heat-treated at the same temperature over the entire length of the film, and the heat shrinkage behavior becomes uniform. To reduce the fluctuation of the film surface temperature, for example, install an inverter to control the wind speed of the hot air that heats the film and suppress the fluctuation of the wind speed, or a heat source of 50 kPa or less (5 kgf / c
It is advisable to use equipment that can suppress temperature fluctuations of hot air by using low-pressure steam of m ² or less).

As a stretching method, not only transverse uniaxial stretching with a tenter but also longitudinal stretching of 1.0 to 4.0 times, preferably 1.1 to 2.0 times may be performed. Good. When biaxial stretching is performed in this way, either sequential biaxial stretching or simultaneous biaxial stretching may be performed, and re-stretching may be performed as necessary. Further, in the sequential biaxial stretching, the stretching order may be any of vertical and horizontal, horizontal and vertical, vertical and horizontal vertical, horizontal and vertical, and the like.

The internal heat generation of the film due to stretching is suppressed,
Focusing on the point of reducing the film temperature unevenness in the width direction,
The heat transfer coefficient in the drawing process is 0.00377 J / cm ² ·
sec ・ ° C (0.0009 calories / cm ²・ sec ・
C.) or higher is preferable. 0.00544-0.
00837 J / cm ² · sec · ° C (0.0013 ~
0.0020 calories / cm ² · sec · ° C) is more preferable.

The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, but when it is applied to a label for a cap seal, for example, it is 10 to 200 μm.
Is preferable and 20-100 micrometers is more preferable.

The cap seal label is prepared by forming a tubular body by rolling the film into a cylindrical shape so that the maximum shrinkage direction of the heat-shrinkable polyester film of the present invention is the circumferential direction and adhering the ends together. It is created by further cutting this into a predetermined length. The method of adhesion is not particularly limited, but the solvent adhesion method is convenient. Adhesive solvents include aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene; halogenated hydrocarbons such as methylene chloride and chloroform; phenols such as phenols; furans such as tetrahydrofuran; 1,3-dioxolane. Organic solvents such as oxolanes are used, among which 1,3-dioxolane is preferable from the viewpoint of safety.

If the adhesiveness of the adhesive portion is poor, the production efficiency will be poor.
Become. For this reason, the film is attached at the adhesive part to the label.
It is preferable that the adhesive part after peeling is less likely to peel off.
Then, the degree of difficulty of peeling of the adhesive part is defined as "adhesive part retention rate".
(%) ”, And that the retention rate is 95% or more
It was a preferable requirement. The measuring method of the adhesive part retention rate is as follows.
Is the same process as when measuring residual shrinkage.
Is. In addition, heat-shrink and cap seal in one step.
In this case, the retention rate of the adhesive portion may be measured under the following conditions. Heat shrinkable film (unshrinked) at a temperature of 30 ± 1 ℃
After leaving for 250 hours in a thermo-hygrostat at a temperature of 85 ± 2%
Use a tube forming device to project one end of the film.
A little inward from the edge of one side of the 2, 1,3-dioxolane 2
mm width, immediately roll the film and overlap the edges.
They are bonded together and processed into a tubular body. This is cut, and the fold diameter (tube) as shown in Fig. 1 (a) is cut.
Label 1 with a length of 87 mm and a length of 53 mm
create. The maximum contraction direction is the circumferential direction of the label. As shown in FIG. 1B, a metal cylinder 2 having a diameter of 46 mm
(Hatch part), 190 ° C for 2 seconds
Heat shrink. At this time, L in FIG. ₁Is 4
7mm, 6mm long film above the metal cylinder 2
Shrink the film over the metal cylinder 2 so that it protrudes.
And let L₁Is 47 mm, L₂Is 6 mm, and the adhesion area is
A preform body having a width of 5 mm is formed. Are performed for 200 samples. For all samples, check the adhesion state and strength of the adhesive part as follows.
Judge by the standard. In the upper part 3a of the adhesive part in FIG. 1 (b)
If peeling occurs (Fig. 2 (b)),
When peeling occurs in the lower part 3b of the adhesive bond (Fig. 2
(A)), or if peeling occurs on the whole, yes
Is light by hand on the upper part 3a and / or the lower part 3b of the adhesive part.
If it can be peeled off, it is regarded as defective. Other than these
Is a pass. And the retention rate (%)
calculate. In other words, the retention rate is the non-defective rate in the primary shrinkage.
(%) Can also be said. Retention rate (%) = 100 x (number of measurements-number of defects) / number of measurements

The cap seal label of the present invention can be used in any of the methods of contracting in a single step, primary contraction and secondary contraction, and has sufficient contraction force, beautiful appearance and contracted finish. Indicates. When applying a cap seal, in the case of contracting in a single step, in the case of undergoing primary contraction and secondary contraction,
The temperature and time conditions may be appropriately set depending on the type of container, the polyester composition of the label, and the like.

[0065]

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modifications made within the scope of the present invention are included in the present invention. Be done. The methods for measuring the composition and physical properties of the chips and films obtained in Examples and Comparative Examples are:
It is as follows.

(1) Film composition Dicarboxylic acid component, polyhydric alcohol component sample (chip or film), chloroform D (manufactured by Eurysop Co.) and trifluoroacetic acid D1 (manufactured by Eurysop Co.) at 10: 1 (volume ratio). A sample solution was prepared by dissolving in a mixed solvent, and NMR (“GEMINI-2
00 ”; manufactured by Varian Co., Ltd.) at a temperature of 23 ° C. and an integration number of 64
Was measured. Based on the peak intensity of the proton measured by NMR, the constituent ratio of the monomers constituting the sample was calculated.

Na, Mg contained in the metal component sample (chip or film),
The contents of and P were measured according to the method described below.

2 g of a [Na] sample was placed in a platinum crucible and ash decomposed at a temperature of 500 to 800 ° C., and then hydrochloric acid (concentration: 6
(mol / L) was added and evaporated to dryness. The residue is 1.
It was dissolved in 10 ml of 2 mol / L hydrochloric acid, and the Na concentration was measured (calibration curve method) using an atomic absorption spectrometer [“AA-640-12”; manufactured by Shimadzu Corporation).

2 g of the [Mg] sample was put in a platinum crucible, ash decomposed at a temperature of 500 to 800 ° C., and then hydrochloric acid (concentration: 6
(mol / L) was added and evaporated to dryness. The residue is 1.
Dissolve in 10 ml of 2 mol / L hydrochloric acid and change the Mg concentration to IC
The measurement (calibration curve method) was performed using a P emission spectrometer [“ICPS-200”; manufactured by Shimadzu Corporation].

Using the [P] sample, the phosphorus component in the sample was converted to orthophosphoric acid by any of the following methods (A) to (C). This orthophosphoric acid was reacted with molybdate in sulfuric acid (concentration: 1 mol / L) to form phosphomolybdic acid, and then hydrazine sulfate was added for reduction. The concentration of the resulting heteropoly blue was measured by an absorptiometer [“UV-150-0
2 "; manufactured by Shimadzu Corporation] was used to measure the absorbance at 830 nm (calibration curve method). (A) Put a sample and sodium carbonate in a platinum crucible and dry-ash decompose (B) Wet decomposition in sulfuric acid / nitric acid / perchloric acid system (C) Wet decomposition in sulfuric acid / perchloric acid system

(2) Residual amount of solid matter (foreign matter) 2 g of a sample (chip or film) was dissolved in a mixed solution of phenol and tetrachloroethane [volume 100 ml; phenol / tetrachloroethane = 3/2 (mass ratio)], and This solution was filtered through a Teflon (registered trademark) membrane filter (pore size: 0.1 μm) to collect a solid, and the residual solid amount was evaluated based on the following criteria.

No: Foreign matter remaining on the membrane filter after filtration cannot be visually confirmed Minor: Foreign matter remaining on the membrane filter after filtration was visually confirmed, and foreign matter was locally present. Many: After filtration When the relics remaining on the membrane filter are visually inspected, foreign matter is confirmed on the entire surface of the filter.

(3) Melt specific resistance value Sample (chip or film) melted at a temperature of 275 ° C.
A pair of electrode plates was inserted therein, and a voltage of 120 V was applied. The current is measured, and the melting specific resistance value (S
i; unit Ω · cm) was determined. Si (Ω · cm) = (A / I) × (V / io) [where A is the electrode area (cm ² ), I is the interelectrode distance (cm), and V is the voltage (V) ), And io represents current (A)]

(4) Castability An electrode made of a tungsten wire is provided between the T die of the extruder and the casting roll whose surface temperature is controlled at 30 ° C., and a 7-1 wire is placed between the electrode and the casting roll.
A voltage of 0 kV was applied. Temperature of resin from T-die 2
A film having a thickness of 180 μm was manufactured (casting speed = 30 m / min) by melt-extruding at 80 ° C., contacting the extruded film with the electrode, and then cooling with a casting roll. The pinner bubbles generated on the surface of the obtained film were visually observed and evaluated according to the following criteria. ○: No pinner bubble generation △: Partial pinner bubble generation was observed ×: Large pinner bubble generation

(5) Heat shrinkage film was cut into a 10 cm × 10 cm square,
After immersing in warm water of ℃ ± 0.5 ℃ or 85 ℃ ± 0.5 ℃ for 10 seconds under no load condition to heat shrink,
It is a value obtained by measuring the lengths in the vertical and horizontal directions of the sample after immersing it in water at 0.5 ° C. for 10 seconds and according to the following formula. Thermal shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

The direction with the highest shrinkage was defined as the maximum shrinkage direction, and the direction orthogonal to this direction was defined as the direction orthogonal to the maximum shrinkage direction. The heat shrinkage in the maximum shrinkage direction at 65 ° C and the heat shrinkage in the maximum shrinkage direction at 85 ° C and 85 ° C were measured.
Is the heat shrinkage ratio in the direction orthogonal to the maximum shrinkage direction.

(6) Thickness distribution film has a length in the maximum shrinking direction of 50 cm and a width of 5 cm
It was cut so as to be (sample for thickness measurement). Ten samples were prepared, and a contact-type thickness meter ["KG6
0 / A ”; manufactured by Anritsu Co., Ltd.], the thickness was measured in the length direction, the thickness distribution was determined based on the following formula, and the average value of all the samples was used as the film thickness distribution. Thickness distribution = (maximum thickness-minimum thickness) / average thickness x 100

(7) Adhesive part retention rate The heat-shrinkable film (unshrinked) was left in a thermo-hygrostat at a temperature of 30 ± 1 ° C. and a humidity of 85 ± 2% for 250 hours, and then taken out, and a tube-shaped molding apparatus was used. Using 1,2-dioxolane 2 inwardly from the edge of one side of the film
It was applied in a width of mm, the film was immediately rolled, and the ends were overlapped (the overlapping length of the adhesion part = 5 mm) and adhered to form a tubular body. This was cut into a label 1 having a folded diameter (half the circumference of the tube) of 87 mm and a length of 53 mm as shown in FIG. The maximum contraction direction is the circumferential direction of the label. As shown in FIG. 1B, a metal cylinder 2 having a diameter of 46 mm
It was covered with (hatching part) and heat-shrinked at 190 ° C. for 2 seconds. At this time, the film was put on the metal cylinder 2 and contracted so that L ₁ after contraction in FIG. 1 (b) was 47 mm and L ₂ after contraction was 6 mm (preform molding). Were performed on 200 samples. With respect to all the samples, the condition and strength of the bonded portion were judged according to the following criteria. When peeling occurs at the upper portion 3a of the adhesive portion in FIG. 1 (b) (FIG. 2 (b)), when peeling occurs at the lower portion 3b of the adhesive portion in FIG. 1 (b) (FIG. 2).
(A)), or when peeling occurred on the whole, or when the upper part 3a and / or the lower part 3b of the adhesive part was lightly peeled off by hand, all were regarded as defective. In all other cases, the test was accepted. Then, the retention rate (%) was calculated by the following formula. Retention rate (%) = 100 x (number of measurements-number of defects) / number of measurements

(8) Primary Shrinkage Finishability With respect to the label (preform) after the primary shrinkage evaluated in the above (7), the shrinkability and finishability of the entire label including the adhesive portion were visually evaluated on a scale of 5 (measurement number). 200).
The criteria are as follows. 5: Best finish, 4: Good finish, 3: Some defects (within 2 places), 2: Defects (3 to 5 places), 1: Many defects (6 places or more), 4 or more pass level Those of 3 or less were regarded as defective. It should be noted that the defects collectively refer to jumping up, wrinkles, insufficient shrinkage (see FIGS. 2C to 2E above), label edge folding, and shrinkage whitening. The defect rate was calculated by the following formula. Primary shrinkage finishability defect rate (%) = 100 × number of defects / number of measurements

(9) Secondary Shrinkage Finishability Total number of labels (preforms) evaluated in (8) above (2
00) was attached to a glass container (used in "Caldas" manufactured by Morinaga Milk Co., Ltd.) and passed through a steam-type shrink tunnel at 90 ° C for 5 seconds to visually determine shrink finish. . Shrinkage finish was performed in the same manner as in (8), and the percent defective was also determined.

(10) Residual (after preforming) shrinkage rate The steps similar to those in the measurement of the adhesive portion retention rate were carried out, and the label was primarily shrunk. After that, the adhesive portion of the label (preform) after shrinkage was cut off, and the sample was cut out so that the maximum shrinkage direction (circumferential direction) of the label was 100 mm and the direction orthogonal to this maximum shrinkage direction was 40 mm, and 75 ±
After immersing in warm water of 0.5 ° C for 10 seconds under no load condition to cause heat shrinkage, in water of 25 ° C ± 0.5 ° C under no load condition 1
The length in the maximum shrinkage direction after immersion for 0 seconds was measured, and the residual shrinkage rate (%) was calculated by the following formula. Residual shrinkage rate = 100 x (length before shrinkage-length after shrinkage)
÷ (length before shrinkage)

Synthesis Example 1 (Synthesis of Polyester) In an esterification reaction can, 57036 parts by mass of terephthalic acid (TPA), 35801 parts by mass of ethylene glycol (EG), and 15843 parts by mass of 1,4-cyclohexanedimethanol ( CHDM) is charged, 0.25M
The esterification reaction was performed by adjusting the pressure to Pa and stirring at a temperature of 220 to 240 ° C. for 120 minutes. The pressure in the reaction vessel is restored to normal pressure, and 6.34 parts by mass of cobalt acetate / tetrahydrate (polymerization catalyst; 20 ppm of Co), 8 parts by mass of titanium tetrabutoxide (polymerization catalyst; 15 pp of Ti)
m), and 132.39 parts by mass of magnesium acetate.
Tetrahydrate (alkaline earth metal component), 5.35 parts by mass sodium acetate (alkali metal component), and 61.5 parts by mass trimethyl phosphate (phosphorus component) were added, and the mixture was stirred at a temperature of 240 ° C. for 10 minutes. The pressure was reduced to 0.5 hPa over 75 minutes and the temperature was raised to 280 ° C. Stirring was continued (about 40 minutes) at a temperature of 280 ° C. until the melt viscosity reached 7,000 poise, and then the mixture was discharged into water in a strand form. Polyester chips A were obtained by cutting the discharged material with a strand cutter (intrinsic viscosity: 0.77 dl / g).

Synthesis Examples 2 to 8 By the same method as in Synthesis Example 1, polyester chips BF shown in Table 1 were obtained. In the production of the chip C of Synthesis Example 3, antimony trioxide was added as a polymerization catalyst to Sb.
Was 160 ppm (based on mass). Further, in Synthesis Examples 4 and 5, titanium tetrabutoxide was used as a polymerization catalyst so that Ti would be 90 ppm (mass standard). Furthermore, in Synthesis Example 6, antimony trioxide was used such that Sb was 260 ppm (mass basis).

[0084]

[Table 1]

In Tables 1 and 2 (described later), the content of the inorganic components (Na, Mg, P) is shown by the concentration of each atom (unit: ppm; mass basis). The origin of each inorganic component is as follows. Na: Mainly derived from sodium acetate Mg: Mainly derived from magnesium acetate tetrahydrate P: Mainly derived from trimethyl phosphate In the table, the abbreviations have the following meanings. TPA: terephthalic acid EG: ethylene glycol CHDM: 1,4-cyclohexanedimethanol BD: 1,4-butanediol NPG: neopentyl glycol DEG: diethylene glycol ε-CL: ε-caprolactone

Example 1 Each chip obtained in the above synthesis example was separately predried to obtain 50% by mass of chip A, 30% by mass of chip C, and chip E.
Is mixed at a ratio of 20% by mass, and 2
Melt extruded at 80 ° C, then rapidly cooled to a thickness of 220μ
An unstretched film of m was obtained. This unstretched film is
After preheating at 20 ° C. for 20 seconds, it was stretched 4.0 times in the transverse direction at 66 ° C. using a tenter, and then heat-treated at 72 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 55 μm. . Table 2 shows the composition and physical properties of the dicarboxylic acid component and the polyhydric alcohol component in the obtained film.

Example 2 Each of the chips obtained in the above synthesis example was separately predried to obtain 60% by mass of chip A, 10% by mass of chip C, and chip D.
In an amount of 15% by mass and Chip F in a ratio of 15% by mass,
It was melt extruded at 280 ° C. using a single-screw extruder and then rapidly cooled to obtain an unstretched film having a thickness of 220 μm. This unstretched film was preheated at 83 ° C. for 10 seconds, then stretched 4.0 times in the transverse direction at 68 ° C. using a tenter, and then heat-treated at 75 ° C. for 10 seconds to give a heat shrinkability of 55 μm. A polyester film was obtained. Table 2 shows the composition and physical properties of the dicarboxylic acid component and the polyhydric alcohol component in the obtained film.

Comparative Example 1 Each of the chips obtained in the above synthesis example was preliminarily dried separately to obtain 30% by mass of chip C, 27% by mass of chip D and F of chip F.
Was mixed at a ratio of 43% by mass, and the mixture was mixed with a single-screw extruder to 2
Melt extruded at 80 ° C, then rapidly cooled to a thickness of 220μ
An unstretched film of m was obtained. This unstretched film is
After preheating at 20 ° C. for 20 seconds, it was stretched in the transverse direction by 4.0 times at 68 ° C. using a tenter, and then heat-treated at 74 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 55 μm. . Table 2 shows the composition and physical properties of the dicarboxylic acid component and the polyhydric alcohol component in the obtained film.

Comparative Example 2 Each of the chips obtained in the above synthesis example was separately pre-dried to give 57% by mass of chip B, 33% by mass of chip C and D.
Is mixed at a ratio of 10% by mass, and the mixture is mixed with a single-screw extruder to 2
Melt extruded at 80 ° C, then rapidly cooled to a thickness of 220μ
An unstretched film of m was obtained. This unstretched film is
After preheating at 20 ° C. for 20 seconds, it was stretched in the transverse direction by 4.0 times at 70 ° C. using a tenter, and then heat-treated at 74 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 55 μm. . Table 2 shows the composition and physical properties of the dicarboxylic acid component and the polyhydric alcohol component in the obtained film.

Comparative Example 3 Each of the chips obtained in the above synthesis example was preliminarily dried separately to obtain 13% by mass of Chip A, 57% by mass of Chip C and D.
Is mixed at a ratio of 30% by mass, and 2 is mixed by using a single-screw extruder.
Melt extruded at 80 ° C, then rapidly cooled to a thickness of 220μ
An unstretched film of m was obtained. This unstretched film is
After preheating at 20 ° C. for 20 seconds, it was stretched in the transverse direction by 4.0 times at 67 ° C. using a tenter, and then heat-treated at 72 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 55 μm. . Table 2 shows the composition and physical properties of the dicarboxylic acid component and the polyhydric alcohol component in the obtained film.

[0091]

[Table 2]

[0092]

According to the heat-shrinkable polyester film of the present invention, since it contains a predetermined amount of 1,4-cyclohexanedimethanol component, the heat-shrinkable polyester film has sufficient shrinkage force as a label for a cap seal, Has excellent retention and shrink finish. In addition, since the film having excellent uniformity of thickness distribution can be obtained by setting the melting specific resistance value to a predetermined value or less, shrinkage unevenness does not occur and the appearance becomes more beautiful. Therefore, the heat-shrinkable polyester film of the present invention can be suitably used as a label for a cap seal.

[Brief description of drawings]

FIG. 1 (a) is an explanatory view showing a tubular label obtained by adhering ends of films to each other, and FIG. 1 (b) is a state in which the label is covered with a metal cylinder to be primarily contracted.

2 (a) to 2 (e) are explanatory views of a defective state of the label after the primary shrinkage, where (a) shows lower peeling, (b) shows upper peeling, and (c) shows jumping up. (d) shows wrinkles and (e) shows insufficient shrinkage.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C08L 67:02 C08L 67:02 (72) Inventor Yoshinori Takekawa 2-1-1 Katata, Otsu City, Shiga Prefecture No. Toyobo Co., Ltd. Research Institute (72) Inventor Katsuya Ito 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Institute (72) Inventor Shigeru Yoneda 2-8 Dojimahama, Kita-ku, Osaka No. Toyobo Co., Ltd. In-house (72) Inventor Katsuhiko Nose 2-2-8 Dojimahama, Kita-ku, Osaka Toyobo Co., Ltd. In-house F-term (reference) 3E084 AA02 AA12 AB01 BA01 BA08 CA01 CB01 DA01 DB01 DC03 FA09 FD09 GB30 3E086 AB03 AC11 AD16 BA02 BA13 BA15 BA33 BB67 CA40 4F071 AA44 AA45 AA46 AA88 AF36 AF58 AF61 AH06 BB06 BB07 BC01 BC12 4J029 AA03 AB07 AD01 AE03 BA03 BA04 BA07 BA09 BA10 BD04A BF09 BF18 BF23 BF24 CA02 CA04 CA05 CA06 CB03A CB05A CB05B CB06A CC05A CC06A JA081 JA091 JA111 JA121 JA231 JA251 JA261 JC411 JC481 JC531 JC571 JF031JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF041 JF1411

Claims (7)

[Claims] 1. A heat-shrinkable polyester film, wherein 1,4-cyclohexanedimethanol component is 5 mol% or more out of 100 mol% of polyhydric alcohol component, and heat shrinkage is cut into a square of 10 cm × 10 cm. Regarding the sample of the water-soluble polyester film, the following (A),
The heat shrinkage rates of (B) and (C) are (A): 15-40
%, (B): 45 to 67%, (C): 8% or less, (A): Immersed in warm water at 65 ° C. for 10 seconds and then pulled up, then immersed in water at 25 ° C. for 10 seconds and pulled up. (B): heat shrinkage in the maximum shrinkage direction when immersed in warm water at 85 ° C for 10 seconds and then pulled up by immersion in water at 25 ° C for 10 seconds and then pulled up , (C): heat shrinkage in a direction orthogonal to the maximum shrinkage direction when immersed in warm water of 85 ° C. for 10 seconds and pulled up, then immersed in water of 25 ° C. for 10 seconds and melted, temperature 275 ° C. Specific resistance value is 0.70 × 10 ⁸
Ω · cm or less, the tube-shaped label formed by adhering the film end portions to each other is first shrunk in hot air at 190 ° C. for 2 seconds by a predetermined method, and then immersed in warm water at 75 ° C. for 10 seconds. Pull up,
A heat-shrinkable polyester film having a heat shrinkage in the maximum shrinkage direction of 10% or more when immersed in water at 25 ° C. for 10 seconds and pulled up. 2. The heat-shrinkable polyester film according to claim 1, wherein the adhesive state retention rate of the adhesive portion after the primary shrinkage of the tubular label is 95% or more. 3. The displacement of the thickness of the film with respect to the maximum shrinkage direction is determined by the length in the maximum shrinkage direction being 50 cm and the width being 5 c.
The heat-shrinkable polyester film according to claim 1 or 2, which has a thickness distribution represented by the following formula of 5% or less when measured using a test piece of m. Thickness distribution = (maximum thickness-minimum thickness) / average thickness x 100 4. The proportion of the 1,4-cyclohexanedimethanol in 100 mol% of the polyhydric alcohol component is 10 to 10.
It is 80 mol%, The heat-shrinkable polyester film according to any one of claims 1 to 3. 5. The alkaline earth metal atom M ^{2 in the} film.
And the mass ratio (M ² / P) of the phosphorus atom P is 1.2 to 5.
The heat-shrinkable polyester film according to any one of claims 1 to 4, which is 0. 6. The content of the alkali metal atom M ^{1 in} the film is 5 to 100 ppm (mass basis).
The heat-shrinkable polyester film according to any one of 5 above. 7. A tubular label for a cap seal, which is obtained by adhering the end portions of the film according to claim 1 to each other.